[Ibrîniðilpathânezel]

I may have missed this in my reading of the topic (wonderful sinus infection, snurfle), but it seems to me that the Nazgul, and the Witch King in particular, have a powerful reason to be afraid of Frodo at Weathertop. The WK knows the prophecy that no Man will slay him -- and here stands a hobbit, armed with an Elvish blade, calling upon Elbereth, ready to take a poke at him. It would seem ludicrous if not for the fact that on the whole, the Nazgul are bullies, maintaining power through fear, and like all bullies, they are thrown for a loop when their targets suddenly stand up and start to fight back. Frodo is a creature comparatively new to the Nazgul; how many hobbits can they have seen before they left Mordor? (And we know that they have already demonstrated that they cannot be bought, and they will show resistance when threatened, via Farmer Maggot, at least.) This is a new race to them, and though they are small, the Nazgul probably know that one of their general kind survived the dungeons of Barad-dur (I'm going from memory here, and it's a bit foggy today, but I seem to recall Tolkien saying that Sauron didn't give up on Gollum just because he didn't know more details about Baggins and the Shire; he could not break his will, such was the nature of hobbit-kind). Gollum also had possession of the One Ring for centuries, and never faded into a wraith, as the Nazgul themselves already had, long ago. Knowing these things and little else about hobbits, I would think they would want to tread carefully around them. A small creature daring to wave a sword at them would be laughable in other circumstances, but in these, especially with Frodo in possession of the One -- their ultimate master -- I believe the Nazgul would have great reason not to laugh. Rather like the ruffians in the Shire, they were not used to the sight of "fearless hobbits with bright blades."

In general, it seems to me that their attacks are not those of people in a confident position of strength; they are attacks of bullies who rule through fear. And that kind of power is always undermined when faced with true courage. Just my two cents, as ever.